Electro-magnet



I (No Model.)

B. THOMSON.

ELEOTRO MAGNET.

No 350,957. Patented Oct. 19, 1886.

WITNESSES: 1 IIVVEIVTOI? W:: /5@/w BY A 770mm N. PETER3.Pholc-lilhcgnpher. washm wn. D. c.

UNITED STATES PATENT Grricn.

EL'IHU THOMSON, OF LYNN, MASSACHUSETTS.

ELECTRO-MAGNET.

SEOIFICATION forming part of Letters Patent No. 350,957, dated October19, 1886.

Serial No. 190,405. (X0 model.)

To ctZZ whom it may concern:

Be it known that I, ELIHU THOMSON, a citi zen of the United States, anda resident of Lynn, in the county of Essex and State of Massachusetts,have invented certain. new and useful Improvements in Electro-Magnets,of which the following is a specification.

Myinvention relates to electro-magncts; and its objects are, first, tosecure by a very simple construction a practically uniform attraction inthe various positions of the parts for any given magnetic excitation.

A further object of myinvention is to cause the parts to move step bystep, or in such way that equilibrium shall be attained at certaindefinite points only in the range of movement of the parts, and at anyintermediate point the want of equilibrium shall cause the parts to movein one direction or the other to one of their definite positions.

The latter part of my invention is especially applicable to the kinds ofmagnet in which the two polar or magnetic portions do not move directlytoward one another-as, for instance in a line perpendicular to thepole-face of the magnet-corcas is the case with an ordinaryelectro-magnet, but at an angle to one anotherthat is to say, in suchway that the line of movement of one part prolonged would cut the planesurface of the other extended or not. The class of magnets to which Ihere specially refer might be also defined as onein which the movementof bodily translation of one or the other of the two polar or attractingportions, either backward or forward, under variations of magneticinfluence, is always greater for any given movement of translation thanis the extent of approach or recession of the polar or attractingsurfaces.

In the accompanying drawings, Figure 1 is a perspective view of anelectro-magnet embodying my invention. Fig. 2 is aside elevation of thesame with the magnet-coil removed. Fig. 3 shows in detail the two polaror attracting portions of the eleetro-magnet-to wit, the pole end of themagnet-core and the iron armature in the field of said pole end. Figs.at, 5, 6, 7, 8, 9, 10, and 11 illustrate in side view and frontelevation various forms of my invention.

Referring to Fig. 1, C 0 indicate the coils of an electromagnet, ill M,of the ordinary form, and Y the usual iron yoke connecting the rear endsof the two cores or legs of the magnet.

A indicates the armature, which is mounted on two arms, 13 B, extendingalong the sides of the magnets, and pivoted 011 suitable bearings orpivots, P P, mounted on the yoke Y Y or adjacent thereto in about thepositions shown. he armature, it will be evident, will move transverselyto the magnetic axes of the magnetcorcs, and, with proper arrangement ofthe parts, will move by the pole ends. The magnet-pole M is cut away orformed at its lower portion or side in such way that when the armatureis retracted or in the position shown the distance between the polar orattracting surfaces of the core and armature shall be at a maximum,while as the armature rises the distance shall decrease, as indicated bythe dotted lines, the outline or curve of the pole-face being, however,such that its curve shall become more and more nearly (proceedthe pathdescribed by the armature. The outline or shape of the pole-face of thecore (or of the armature, as will be presently seen) can be readily madesuch that a practically uniform pull or attraction exists throughout therange of motion of the armature, at the same time that the force of theattraction very considerable and the swing of the armature large. Tosecure this result it is only necessary that the curved surfaces of thepole and armature presented to each other shall c011- tinue to approachbut never touch, and at the same time that the direction of the lines ofcontour of the pole shall approach more and more nearly to parallelismwith the curve of the swing of the armature. This is indicated inalarger way in Fig. 3. It is not necessary that the armature A be around bar, as it can be shaped in many other ways, one of which isindicated in Fig. l, where its nearest side presented to the magnet M isrounded, while its remote side is square.

For many purposes it is desirable that the magnet shall not only possessuniform or nearly uniform power throughout its range of 1 movement, butthat it shall also move in such ing upwardly) parallel to the curveindicating range step by step. I secure this action by notching orgrooving the face of the magnetpole or armature, when suitably arranged,so

that the magnet-faces opposed shall not present a continuous line, butshall have depressions and elevations, while the general contour of thefaces is preserved. One of the ways of securing this is indicated inFig. 5, where a number of small grooves, V V V, are cut across the faceof the magnet, as shown. The grooves at that portion of the pole towardwhich the armature approaches very closely must be very small andshallow, while those at the portion where the armature is more distantcan be quite large in comparison. If we now assume that a certain degreeof energization exists in the magnet-pole M, the armature, being inequilibrium below the lower groove, should, if the parts are properlyshaped, be capable of remaining in equilibrium between any two groovesor above the upper groove with the same energization or power of thepole M. It will not, however, remain in equilibrium opposite any one ofthe grooves, but will pass either above or below the same. I call this astep-by-step magnet because in exerting its attraction it imparts motionof a step-by-step character.

Fig. 7 shows a modification of the magnetpole and armature in which theface of the pole M is itself rounded and the shape of the opposing faceof the armature is made such that in the latters passage over the poleby a swing in an are, as before, the lower portions of the armature comegradually nearer and nearer to the projecting surface of the magnet poleand give the same effects as in the arrangement shown in Figs. 3 and 4,except that the shape of the magnet-pole has now been conferred upon thearmature and the shape of the armature has been conferred upon themagnetpole. The grooves for the step-by-step action can likewise begiven to the armature, as seen in'Fig. 8.

As an illustration of the utility of astep-bystep magnet, I have shownit in Fig. 9 applied to adjusting a variable resistance, R, in which aseries of contact-plates are traversed by a contact carried by thearmature A. Now, it is oftentimes desirable that the contact-plate Jshould not rest on the break between any of the contact-plates of thevariable resistance, as from such action uncertain contact may resultand a burning of the plates or the traveling piece J may follow. If,now, the positions of equilibrium of the armature A before themagnet-pole M correspond to the positions at which the piece J isresting upon the contactplates, singly, it is evident that the magnetwill serve to adjust the resistance R during the movement of itsarmature step by step, and will not permit the contact J to makeuncertain contact with one or two plates.

It is obvious that by simply grooving the pole-face, as indicated inFigs. 5 and 6, the portions of the pole-face between said groovesconstitute attracting projections systematically disposed so as to causethe armature to come to rest at certain definite positions in its rangeof movement, which positions depend upon the number and location of theattracting projections. In other words, the attract ing projections givean increased pull upon the armature in certain definite positions, whilein those portions of the range of movement of said armature between saidpositions there is a lesser pull, &c., the result being that thearmature cannot rest in the latter positions, but will be caused to takepositions corresponding to the location of the attracting projections.

Instead of forming grooves in the pole-face, it is obvious that the sameeffect may be attained by forming upon the pole a series of very slightprojecting studs or knobs, as indicated in Figs. 10 and 11, which ofthemselves are sufficient to cause the armature to hesitate or stop inits motion slightly at different points in its swing.

It will be evident that numerous changes in the configuration of theface of the magnet or its armature to secure the result described may bemade, and that, so far asthe feature of step-by-step action of themagnet goes, it might be applied without change of principle to manyexisting forms of magnets giving a prolonged range of action.

What I claim as my invention is l. The combination, with anelectro-magnet, of a reciprocating armature having a rounded face andmoving transversely to the axes of the cores, a frame sustaining saidarmature and pivoted at or near the yoke of the magnet, the poles of themagnet being formed, as described, with a curve gradually approachingthe line of swing of the armature and gradually becoming more nearly butnot quite parallel thereto, as and for the purpose described.

2. A magnet-pole having a series of elevations or projections, arrangedas described, for the purpose of'locating the position of the armatureand securing a step-by-step action of the same.

3. The combination, with an electro-magnet whose attracting polarsurfaces of core and armature approach to or recede from one anotherduring movement to an extent less than the maximum movement of thetranslation of the parts, of a pole-surface having a series ofattracting projections for giving a step-by-step movement to thearmature, as and for the purpose described.

4.. In an electro-magnet having a substantially uniform pull upon itsarmature through its range of movement, an attracting-surface havingsystematically-formed attracting projections, arranged as described, togive a stepby-step movement of the parts, while at the same time servingto hold them in equilibrium in the various positions corresponding tothe said elevations and depressions.

5. The combination, with an electro-magnet having its parts properlymounted to permit the core and armature to gradually approach, i asdescribed, of a pole-surface having a series of attracting projections,as and for the purpose set forth.

6. The combination of an elcetro-niagnct having a curved polar face', anarmature mounted so as to gradually approach said core, and a series ofattracting projections systematically disposed on theattracting-surfaces of core or armature, as set forth.

'7. Thecon1l1 inatio11, with an electro-magnet, of a series ofattracting projections systematically disposed, as described, and ofprogressively less magnitude, as and for the purpose described.

S. The combination, with an electro-magnet, of a series of attractingprojections systematic ally disposed, as described, whereby the movingparts may be caused to move step by step or to assume certain definitepositions through out the range of movement, depending upon the locationof the several projections of the series.

Signed at Lynn, in the county of Essex and State of Massachusetts, this27th day of Jan- 25 nary, A. D. 1886.

ELIHU THOMSON.

lvitnesses:

M. L. THOMSON, J XV. GIBBONEY.

